Apparatus for treating pulverized fuel such as coal and the like



April 10, 1934. FRL. boRNBRoc-:K efr A| APPARATUS FOR TREATINGPULVERIZED FUEL SUCH AS COAL AND THE LIKE 2 Sheets-Sheet l Filed March28, 1931 INVENTORS.

ATTORNEY. i

April 10, 1934. -f 1F. L. BORNABROO'K Er A1. I 1,954,350

APISARATUS FOR TREATING PULVERIZED FUEL SUCH AS -COAL AND THE LIKE FiledMarch 28, 19:51 2 sheets-sheet 2 'IIL llsll lll A TTORNE Y.

Patented Apta i10, 1,934:

APPARATUS FOR TREATING PULVERIZED FUEL SUCH AS COAL AND THE LIKEFrederick L. Dornbrook and Montrose K. Drewry, Milwaukee, Wis.,assignors to The Milwaukee Electric Railway and Light Company,Milwaukee, Wis., a corporation of Wisconsin Application March 28, 1931,serial No. 525,940

s claims. (ci. a-10s) This invention relates to improvements inapparatus for distilling by-products from pulverized coal.

By way of example, in the ordinary power 5 plant for the production ofelectrical energy, fuel is fed to a furnace and burned therein and theheat from the burning `fuel boils water circulating within a boiler andgenerates steam. The steam thus generated is used to operate a steam l0engine, which in turn operates a generator for generating the electricalenergy.

In some power or electrical generating plants it has been foundpractical and advantageous to use pulverized coal as the fuel for thefurnace and boiler, and the present invention has special reference to apower rplant wherein pulverized coal is the fuel utilized. i

In such installations, valuable volatile constituents of coal are burnedin the boiler furnacefor simply their heat value. Since their4 value ascoal gas, coal tar or other by-products, is considerably in excess oftheir heat value, pre-distillation conserves their special utility andrealizes a profit from the process. f

The present invention concernsI itself with an apparatus which may be anadjunct to the regular pulverized coal storage type system in generaluse and has as its primary object the provision of an apparatus forso'utilizing pulverized fuel in a power plant that pre-distillation ofthe fuel may be efficiently and satisfactorily accomplished, so as toproduce and conserve as commercial by-products gas and tar, andpermitting the resultant coke to be used as the fuel for the boilerfurnace.

A further object of the invention is to provide an apparatus which maybe applied to an electrical generating plant wherein a distillingapparatus is interposed between the fuel bunker and the boiler and asfuel is delivered from the bunker to the distilling apparatus the fuelis carbonized and the gases and tars separated therefrom and taken awayand stored for commercial purposes While the residue of coke is feddirectly into the boiler furnace where it burns and furnishes heat forthe boiler.

Most coals, when heated to distillation temperatures, become soft andfuse and cake into larger and rm pieces, which pieces ordinarily clogdistillation equipment unless special attention is exercised. Thepresent invention further provides in a coal distillation apparatus, anovel type of oxidizer, which, in the present equipment, renders thecoal non-caking by thoroughly exposingV it 'to a high temperature gascontaining and important features:

(l) The coal gas distilled from the coal is kept entirely separate fromthe heating gas whereby dilutionof the coal gas is entirely eliminatedand maximum heating value per cubic foot is insured.

(2) Maximum temperatures encountered by 7 0 the coal gas are such thatno thermal decomposip tion occurs which might decrease its heating valueper unit of volume.

(3) Maximum value tars are obtained from the coal gas because the sameare not deteriorated by exposure to high temperatures.

(4) in the present apparatus and method applicable thereto the coal gasis caused to filter through the pulverized coal and into the screenedgas off-take pipes at low velocity whereby the discharged coal gas isexceedingly clean and furnishes `clean tar and gas.

(5) Condensation of volatile products in the gas olf-take system isprevented by the concurrent flow of coal and coal gas because after thegas has been evolved, it must pass through hotter temperatures, insuringnon-deposition of any liquids. y v

A further object of the invention is to provide an apparatus fordistilling by-products from pui verized coal prior to burning the coalin a boiler furnace which is very simple, which is economical andeflicient, and which is well adapted for the purposes described. Y

With the above and other objects in view the invention consists of theimproved apparatus for distilling by-products from pulverized coal, and'Es parts, and combinations, as set forth inthe claims, and allequvalentsthereof.

In the accompanying drawings in which the same reference charactersindicate the same parts in all of the views:

Fig. 1 is a vertical sectional view of a boiler furnace equipped withthe improved distillation apparatus;

Fig. 2 is a vertical sectional view, on a larger scale, of thecarbonizer employed in the present apparatus;

Fig. 3 is a cross-sectional view taken on line 3-3 of Fig. 2 and on alarger scale;

Fig. 4 is an enlarged longitudinal vertical secn tional view of theoxidizer employed in the pres` ent apparatus; and

Fig. 5 is a sectional view thereof taken on line 5-5 of Fig. 4.

Referring now more particularly to the drawings, with special referenceto. Figs. 1, 4 and 5 thereof, it will appear that the numeral 8designates an oxidizer, which oxidizer is in the form of an enclosedtank or container, of a substantial size. One side of the container,toward one end thereof, `and intermediate the upper and lower ends ofthe container, is entered by a pulverized coal inlet pipe 20 whichbranches from a pipe 45 which pipe leads from a coal pulverizer- (notshown). Opposite the coal inlet pipe 20, the container 8 is entered by aflue gas pipe 10. As shown clearly in Fig. 1 the source of the flue gasis the upper portion of the boiler furnace 11. The ilue gas pipe extendsinto the upper portion of the boiler furnace and extends outwardly ofthe boiler furnace into a header 12 and the ue gas pipe 10, of a reduceddiameter, extends from the header 12 into the oxidizer, in the mannerpreviously mentioned, and shown particularly in Figs. 4 and 5. Withinthe lower portion of the container 8, extending lengthwise of the same,is a revolving paddle wheel 13, The revolving paddle Wheel has itscentral shaft portion 14 suitably journaled in bearings in opposite endsof the container and an outwardly projecting portion of the shaft 14carries a pulley wheel l5 about which a belt 16 is extended. The belt isconnected with a suitable source of motive power (not shown).

In the proper functioning of the oxidizer, pulverized coal enters theoxidizer uniformly through the tubularv member 20, and heating andoxidizing flue gas enters the oxidizer through the tubular connection10. The revolving paddle wheel 13 is driven at a desired speed andfunctions to keep the pulverized coal and the introduced heatingandoxidizing gas in constant agitation. Extendingthrough the upperportion of the container 8 is an elongated tubular member 17 and thelower end portion of said member p 1'7, within the container 8 flts intoa vertically adjustable pipe section 18. Adjustable raising and loweringmechanism 19, accessible from exteriorly of the container 8, permits theadjustable extension 18 to be moved with respect to the inner end of themember 17 to locate, as desired, the entrance end of the member 18. Uponstarting the apparatus, coal concentrates in the oxidizer containeruntil the rate of removal equals the rate of supply. The accumulation ofcoal therein increases the time of treatment, which, like temperatureand turbulence, is necessary to destroy the caking properties of thecoal.

The vertically adjustable connection 18 on the pipe 17 is arranged sothat by adjusting the same the y amount of coal accumulation may begoverned, and changes in the-speed of the paddle wheel 13 can accomplishthe same results within certain limits. However, it is obvious thatconcentration of the coal is greatest in the vicinity of the paddlewheel and is the least near the upper portion of the oxidizer container.A steady flow of gas and entrained coal will pass out o f the oxidizerthrough the members 18 and 17.

It has been found that the addition of .from two percenth to ve percentAof oxygen to the weight of the coal will render it non-vcaking upon thecoal being rapidly heated above the distillation temperature. It isdesirable to maintain a lower end of the cyclone collector opens intothe temperature of approximately 600 degrees Fahrenheit Within theoxidizer and this is accomplished by the introduction of the flue gasfrom the boiler furnace, and said ue gas contains from five to tenpercent free oxygen. In addition to the heat derived within theroxidizer from the flue gas, heat is also derived from the chemicalreaction of the coal and oxygen. This together with the vigorousagitation afforded by the paddle wheel will effectively destroy allcaking properties of the coal Within from ten seconds to severalminutes, depending upon the size of the coal particles. Small particlesof coal are swept almost directly through the oxidizer with the heatinggases, while the larger particles, since they are less easily sweptupwardly toward the olf-take member 18, remain within the oxidizer for alonger period. y

Adjustment of the paddle wheel speed and the off-take height of themember 18 governs the accumulation of coal to within certain limits,causing reasonable power consumption of the paddle wheel. The agitationof the coal particles is also important in that relatively fast andconstant movement of the same prevents spontaneous combustion andresultant ring. It should also be observed that the coal and gasoff-take 18-17 is at the end of the tank opposi'.e from that at whichthe coal and gas enter.

The peculiar type of oxidizer employed is important in that it allows acontrollable quantity of coal to accumulate and thereby the availabletime for oxidation maybe set at will. The oxidizer employed also retainslarger coal particles longer than the small particles so that the cakingproperties of all type of particles are reduced to an equal extent. Theoxidizer also obtains the maximum contact of oxygen and coal with aminimum power expenditure. Uniform oxidation of all coal particles isinsured because of the concurrent travel of coal and gas between theinlet and'outlet. Y

A standardcyclone separator 23 is mounted directly over a carbonizermember 21 and the upper portion of said carbonizer. The coal and gasoff-take pipe 17 from the oxidizer extends to and opens into an upperportion of the cyclone collector tangentially. The said cycloneseparator serves to effect a separation of the oxidized coal from theoxidizing flue gas. The efficiency ofthe collector need not be perfectsince dusty gas therewithin leaves the collector through a pipe 24 andsaid pipe extends to a header 25 from which header a pipe 26 leads to aconnection 27 opening into the furnace at the point where the entrainedcoal is burned. The heat value of any volatile products removed in theoxidation process is thus conserved, and the loss to the process is'.negligible. The lower tapered end portion of the cyclone separator isprovided with a rotary feeder 28 through which coal passes and isdischarged from the upper portion of the carbonizer container 2l. The

rotary feeder serves as a positive seal between coal, the steam beingintroduced into the carn., u"

bonizer thrugh the pipe 46.

The carbonizer 21 is in the form of a large container of rectangularform having a lower iapered portion 2l'. Within the lower portion of themain body portion of the enclosure the carbonizl1'.

ing apparatus is disposed. Said carbonizing apparatus comprises aplurality of sheet metal Aheating elements 29 of envelope-like form, asshown most clearly in Figs. 2 and 3. Depending into the container 2 1from the flue gas header 12 are a plurality of flue, gas inlet pipes 30.An end portion of a heating element 29 opens into each ofthe pipes 30 sothat hot flue gas will be introduced into the envelope-like heatingelements 29. The opposite ends of the hea' ing elements open into fluegas outlet pipes 31 disposed within the opposite side of the container21 and said pipes 31 extend upwardly outwardly` o-f the container anddischarge into the header 25 from which the pipe 2 6 exends whichconducts the gases back to the boiler furnace. Baines 32 and 33 arepositioned within the .envelope-like heating elements to cause a. flowof gases therethrough ih the manner indicated by arrows in Fig. 2. Thereare also Within the container 21 forming part of the carbonizingapparatus, vertical coal gas off-take pipes 34, which pipes areperforated and covered with fine screen throughout their length. Thelower end portions of said pipes 34 connect with horizontal coal gasmanifolds 35, which mani- .folds discharge'info a coal gas off-takeheader 36 extended exteriorly of the container 21.

. With reference to Fig. 1, it will appear that pulverized coalbraneh'pipes 20 lead off from the pipe 45, the upper branch pipe 20extending to the oxidizer and the lower pipe 20 extending to a the binportion .of the carbonizer 21. VNormally the lowermost valve 22 isclosed and therefore all the pulverized coal is directed into theoxidizer and is treated there before reaching the bin 21. This is thecase during usual distillation operations. However, if forany reason thedistillation apparatus .is not functioning, then the upper valve 22 isclosed and the lower valve 22 is opened, whereby untreated pulverizedcoal is routed direct to said bin or container 21. In this event no heatis applied to the carbonizer plates and the operation of the apparatusis the same as that practiced in similar apparatuses having nodistillation apparatus incorporated therewith.

In the functioning of the carbonizen oxidized coal at approximately 600degrees Fahrenheit settles slowly downwardly past the heating elements29, which heating elements heat the coal beyond the primary distillationzone of about 700 degrees Fahrenheit to 900 degrees Fahrenheit. Aspreviously mentioned, hot flue gas is used as a convenient med'um and iscaused to flow through the heating elements toheat the dpwiiily'sttliigcoal. Maximum efficiency is gained by having the gas and coal flow inopposite directions, although with the coal.

the gas is confined and does not actually contact Inasmuch as pulverized.coal has relatively low heat transferl characteristics the heatingelements 29, having large surface areas, compensate. for th's. Theabsence of oxygen within the carbonizer eliminates the possibility 'ofoxidation of metal of the heating elements.

`Coal gas is evolved from the coal between the j. heating elements 29and said coal gas travels horizontally to the screened gas off -takepipes 34.

Pulverized coal permits passage of a considerable gas ilow, especiallyupwardly, and a head of coal above the screened open ends of the gasolf-take `pipes effectively seals the same from the steam spacethereabove. Suction .of an exhauster positioned as at 37 in Fig. 2,which acts on the gas off-take pipes, or slight stem -pressure above thecoal within the container 2l, introduced thereinto/ through4 astea-mconnection 46, maintains the gas ow tendency downwardly, but little flowoccurs in this d'rection due to the packing tendency of the coal. -Thecoal gas taken oi through the header 36 is cooled and collected in anystandard apparatus for that purpose (not shown) and tars are condensed.

After carbonization in the member 2l, the vresulting semi-coke, still inpulverized or dust form, gravitates through the lower tapered portion 21of the container to a suitable feeder 38,. which feeder is driven from asuitable source of power (not shown) by a belt 39. `The feeder passesthe sem'-coke dust into the lower vertical tubular connectlon 27 fromwhere it is introduced directly I into the boiler furnace, and withtheintroduced coke, gas, passing through the pipe 26, is also introducedinto the boiler furnace. The introduced semi-coke dust has altemperature of about 1000 degrees Fahrenheit, which compensates for itslreduced volat'le content in facilitating combus-` tion and it is burnedlike untreated coal. The heat generated from said burning'fuel boilswater within a boiler member above the furnace and steam is taken offthrough a pipe 4l for opera-ting any desired equipment.

,In connection with the carbonizing apparatus andthe coal gas off-takeIsystem, it should be noted that the coal gas is maintained entirelyseparately from the heating gas, whereby any dilution of the coal gas iseliminated. The maximum temperatures encountered by the coal gas j aresuch that no thermal decomposition occurs ,i which will decrease itsheating value per unit of volume. Maximum value tars are obtained fromthe'coal gas because there is no deterioration due gases forcarbonization. Due to the slowdownward rate 'of coal travel the time forcarbonization reaction is very ample. The prevention of dei1 teriorationof coal gas and tar products is possi- 'ble because the maximumtemperatures are considerably less than those at which cracking en f"inferior constituents occurs. The facility of lconabustion of the cokeis obtained by reason of the maintenance of the high temperature (about1000 degrees Fahrenheit) as the coke is fed into the furnace.

Although the apparatus of this invention has been described andillustrated as applied to a furnace such as the furnace of asteam-generating plant, theinvention is to be considered as suflitl'..') to exposure to high temperatures. The coal 'gas iieiently broadto include theapparatus when not so used. Obviously the advantages ofthe fuel- 'treatment apparatus including the oxidizer and arbonizer willbe realized insofar as the production of the distilled gasesand powderedcoke is concerned when not used with a furnace. apparatus is merely onewhich is peculiarly adapted with greater advantage for use with afurnace. f

The a From the foregoing description it will be seen that the improvedapparatus for distilling byl' products from pulverized coal is bothsimple and novel and is well adapted for the purposes set forth.

What is claimed as the invention is:

1. In combination with a pulverized fuel combustion chamber and a sourceof Apulverized fuel, connecting means therebetween comprising acarbonizer having heaters therein and an oxidizer, means for feedingfuel to said oxidizer and means for feeding oxidized fuel from saidoxidizer to said carbonizer, means for withdrawing gas from saidcombustion chamber and conveying some of said gas into said heatersinsaid carbonizer and conveying some of said gas into said oxidizer, andmeans for conveying said gas from'said heaters and said oxidizerbacl; tosaid combustion chamber.

2. fn combination with a pulverized fuel combustion chamber and a sourceof pulverized fuel, connecting means therebetween comprising acarbonizer and an oxidizer, means for feeding pulverized fuel to saidoxidizer and means for feeding oxidized fuel from said oxidizer to saidcarboniz`er, means for withdrawing gas from said combustion chamber, andfor conveying oxygenbearing gas in commingling association with saidpulverized fuel in said oxidizer, means for separating said commingledgas and fuel, and means for conveying said gas from said oxidizer backto said combustion chamber.

3. In combination with a pulveriz'ed fuel combustion chamber anda sourceof pulverized fuel, connecting means therebetween comprising acarbonizer having a heater therein and an oxidizer, means for feedingpulverized fuel to said oxidizer, means for feeding oxidized fuel from`said oxidizer to said carbonizer, and means for feeding coke particlesfrom said carbonizer to said combustion chamber, means for withdrawingoxygencontaining gas from said combustion chamber, means for dividingthe withdrawn gas and for conveying some of said gas in comminglingassociation with said pulverized fuel in said oxidizer and for conveyingthe remainder of said gas into said heater in said carbonizer, and meansfor conveying the gas in said oxidizer and the gas in the heater back tosaid combustion chamber.

4. In combination with a pulverized fuel combustion chamber and a.source of pulverzed fuel, connecting means therebetween comprising acarbonizer having a heater therein and an oxidizer, means for feedingpulverzed fuel to said oxidiaer, means for feeding oxidized fuel fromsaid ori-- dizer to said carbonizer, and means for feeding cokeparticles from said carbonizer to said combustion chamber, means forwithdrawing oxygencontaining gas from said combustion chamber, means fordividing the withdrawn gas and for conveying some of said gas incommingling association with said pulverized fuel in said oxidizer andfor conveying the remaining of said gas into said heater in saidcarbonizer, means for conveying the gas in said oxidizer and the gas inthe heater back to said combustion chamber, and means for withdrawingvolatile products of carbonization from said carbonizer.

5. ln. an apparatus for treating pulverized fuel, an oxidizer comprisingan enclosed vessel, a pulverized fuel delivery member entering the lowerend portion of said vessel, an oxidizing and heating gas delivery memberentering the same lower end portion of said vessel, an agitator withinsaid vessel, and a vertically adjustable fuel and gas discharge pipeextending outwardly from the upper opposite end portion of said vessel,said discharge pipe depending into said vessel whereby by adjustment theoutlet end thereof is raised and lowered with respect to the height Iofsaid vessel.

6. In combination, a furnace, an oxidizer, means for introducing astream of pulverized coal froml a source of supply into the oxidizer,means forconveying oxygen-containing flue gas from'zthe furnace to theoxidizer, an agitator within" the oxidizer, ,means for separating fluegas from the coal after the coal has been treated by the former, .acarbonizer, an enclosed heating element therewithin and sealed fromthe'contents of the .interior yof the carbonizer, means for dischargingcoaLseparated from the flue gas into the carbonizer, m'eansfor conveyingiiue gas from the furnace into said'fheating element, said flue gas inthe heatingfelement being maintained isolated from the coal Vin thecarbonizer, means for withdrawing coal gas from the carbonizer, andmeans for conveying powdered carbonized coal directly from thecarbonizer to the furnace.

FREDERICK L. DORNBROOK. MONTROSE K. DREWRY.

